Synthesis and Antiproliferative Activity Evaluation of the Disulfide-Containing Cyclic Peptide Thiochondrilline C and Derivatives

Article abstract of DOI:10.1021/acs.jnatprod.5b00428

Thiochondrilline C (4) was previously isolated from Verrucisispora sp. and reported to have moderate cytotoxicity against human lung adenocarcinoma cells. Herein, we report the synthesis of thiochondrilline C by N-terminal peptide extension, oxidative disulfide bond formation, and heterocycle installation as key steps. Antiproliferative activities for the prepared natural product and several derivatives against the NCI 60 cancer cell line panel are also described. Derivative 22 was identified as a moderately potent antiproliferative agent (50% growth inhibition (GI₅₀) = 0.2-12.2 μM) with leukemia (average GI₅₀ = 1.8 ± 0.1 μM) and colon (average GI₅₀ = 2.4 ± 0.3 μM) cells being most sensitive.

Full text of DOI:10.1021/acs.jnatprod.5b00428

Article
pubs.acs.org/jnp
Synthesis and Antiproliferative Activity Evaluation of the Disulfide-
Containing Cyclic Peptide Thiochondrilline C and Derivatives
Mohana Rao Vippila, Phuong Kim Ly, and Gregory D. Cuny*
Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Science and Research Building 2, Room 549A,
Houston, Texas 77204, United States
*
S Supporting Information
ABSTRACT: Thiochondrilline C (4) was previously isolated from
Verrucisispora sp. and reported to have moderate cytotoxicity against human
lung adenocarcinoma cells. Herein, we report the synthesis of thiochondrilline
C by N-terminal peptide extension, oxidative disulfide bond formation, and
heterocycle installation as key steps. Antiproliferative activities for the
prepared natural product and several derivatives against the NCI 60 cancer
cell line panel are also described. Derivative 22 was identified as a moderately
potent antiproliferative agent (50% growth inhibition (GI ) = 0.2−12.2 μM)
50
with leukemia (average GI = 1.8 ± 0.1 μM) and colon (average GI = 2.4 ±
5
0
50
0.3 μM) cells being most sensitive.
hiodepsipeptides (e.g., thiocoraline A, 1) and other
structurally related depsipeptide natural products (e.g.,
triostin A, 2, and echinomycin, 3) exhibit a broad range of
Thiochondrilline C is a marine-derived natural product
recently isolated from Verrucisispora sp., along with thiocoraline
A. Thiochondrilline C is composed of a disulfide-containing
cyclic peptide with one 3-hydroxylquinaldic moiety and is a
substructure of thiocoraline A, but with a significantly lower
molecular weight (MW = 609 versus 1156). Thiochondrilline C
has been reported to demonstrate moderate cytotoxicity (EC50
T
11
biological activities, including as antitumor, antibiotic, and anti-
1
inflammatory agents. However, clinical advancement of
echinomycin for the treatment of cancer has been hindered
2
by significant dose-limiting toxicities. One of the primary
=
2.9 μM) against human A549 lung adenocarcinoma cells.
obstacles in surpassing this hurdle has been inadequate
availability of derivatives that would permit extensive
structure−activity relationship (SAR) studies to be conducted
in order to optimize the selective toxicity for malignant cells
and to improve physiochemical and absorption, distribution
metabolism, and excretion (ADME) properties. Most of the
current approaches in this field aim to modify their structures
Although the potency of thiochondrilline C is less than
11
thiocoraline A (EC50 = 0.010 μM), its ligand efficiency
defined as the −log IC in molarity/number of heavy atoms)
(
50
is greater (0.14 versus 0.11) due to lower molecular weight. On
the basis of its greater ligand efficiency and synthetic tractability
we sought to develop a versatile synthetic route to thiochondril-
line C that would also be amenable to the preparation of
derivatives to further study the antiproliferative activity and
physiochemical and ADME properties of this natural product
and its non-natural derivatives.
3
,4
through extensive synthesis or to alter biosynthesis pathways
for the generation of thiodepsipeptide and depsipeptide
5
derivatives. However, these strategies will likely produce
equally complex structures with similar liabilities.
Thiocoraline A, isolated from the mycelium of Micro-
monospora sp., has been reported to exhibit potent
antiproliferative activity against an array of cancer cells,
RESULTS AND DISCUSSION
■
6
A divergent approach for the synthesis of thiochondrilline C
was envisioned that consisted of coupling 5 and 6 in the final
step, which would provide efficient flexibility for modification of
the exocyclic portion of the molecule (Scheme 1). Cyclic
intermediate 5 would be prepared by oxidative disulfide bond
formation of 7, which would be generated by N-terminal
peptide extension starting from 8.
An efficient synthesis of 3-hydroxyquinoline-2-carboxylic
acid, 13, was initially developed (Scheme 2). ortho-Nitro-
benzaldehyde, 9, was selectively reduced with iron to provide
including lung, breast, colon, renal, and melanoma (Figure
7
1
). The mechanism of action for thiocoraline A, like many
structurally similar thiodepsipeptides and depsipeptides, is bis-
intercalation-induced DNA damage. Thiocoraline A also has
been reported to inhibit DNA polymerase α and hypoxia-
8
inducible factor 1α (HIF-1α). In addition, preliminary SAR
studies of antiproliferative activity for thiocoraline A and related
molecules have revealed that the 3-hydroxyquinaldic or 2-
quinoxalinecarboxylic substituents are a key contributor to
biological activity by providing a structural motif for DNA
Received: May 13, 2015
9
,10
intercalation.
©
XXXX American Chemical Society and
American Society of Pharmacognosy
A
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
Figure 1. Structures of thiocoraline A (1), triostin A (2), echinomycin (3), and thiochondrilline C (4).
Scheme 1. Retrosynthetic Analysis of Thiochondrilline C
hydrolysis with aqueous potassium hydroxide, which furnished
13 in 92% yield.
The synthesis of cysteine derivative 6 started with N-
methylation of 8 in the presence of NaH and MeI in THF to
14
generate 14 in 69% yield. Compound 14 was treated with
trifluoroacetic acid (TFA) in the presence of triisopropylsilane
(
TIS) to remove the trityl, which was accompanied by loss of
the Boc protecting group. This step was followed by selective S-
methylation with MeI in the presence of sodium bicarbonate,
followed by reintroducing Boc protection of the amine to give
15
1
5 in 51% yield. Acid 15 was treated with thionyl chloride in
methanol to generate 6 in 72% yield.
Assembly of the natural product and derivatives began by
esterification of acid 14 with tert-butyl-2,2,2-trichloroacetami-
date to give the corresponding tert-butyl ester 16 in 85% yield
12
(
Scheme 3). Selective removal of the Boc group with 1 N HCl
ortho-aminobenzaldehyde, 10 (87%). Subsequent condensa-
provided 17 in 84% yield. The secondary amine 17 was coupled
with Fmoc-Gly-OH using 1-ethyl-3-(3-dimethylaminopropyl)-
carbodiimide (EDC) and 1-hydroxy-7-azabenzotriazole
(HOAt) to provide dipeptide 18 in 96% yield. Fmoc removal
tion with ethyl bromopyruvate generated ethyl 3-amino-2-
13
quinolinecarboxylate, 11, in 90% yield. A Sandmeyer reaction
was employed to convert the amine to a hydroxy in 68% yield
in the presence of H SO and sodium nitrite, followed by ester
2
4
Scheme 2. Synthesis of 3-Hydroxy quinoline-2-carboxylic Acid (13) and N-Me-L-Cys(Me)-OMe (6)
B
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
Scheme 3. Synthesis of Thiochondrilline C (4) and Derivatives
from the dipeptide was carried out with piperidine, and
subsequent coupling with Fmoc-D-Cys(Trt)-OH using EDC
and HOAt furnished tripeptide 19 in 77% yield. The tripeptide
was treated with piperidine to remove the Fmoc protecting
group followed by coupling with 3-hydroxyquinoline-2-
carboxylic acid, 13, using EDC and HOAt, which generated 7
in 88% yield. The oxidative disulfide bond formation was
mediated with iodine to afford cyclic peptide 20 in 91%
Thiochondrilline C and two of the other derivatives (5 and 21)
did not show significant activity, including human A549 lung
adenocarcinoma cells (e.g., <30% inhibition of growth at 10
μM). However, derivative 22 demonstrated moderate growth
inhibition (GI) activity against the 60 cancer cell lines (GI50
=
0
.2−12.2 μM), with leukemia (GI50 range = 0.2−5.7 μM;
average GI = 1.8 ± 0.1 μM) and colon (GI range = 0.6−7.9
μM; average GI50 = 2.4 ± 0.3 μM) cells being the most
50
50
1
5,16
yield.
This material was treated with TFA to generate acid
sensitive. Total growth inhibition (TGI) could generally be
5
in 82% yield.
achieved in these cells at ≤10 μM (leukemia: average TGI
=
5
0
Initial attempts to couple acid 5 and the secondary amine 6
7
.5 ± 0.2 μM; colon: average TGI50 = 7.8 ± 0.7 μM).
Derivative 22 was also evaluated in several in vitro ADME
with EDC and HOAt did generate thiochondrilline C, but only
in <10% yield. Efforts to increase the efficiency of this reaction
employing various coupling reagents, such as DCC, HBTU,
HATU, and PyBOP, did not generate the desired product.
However, the coupling reagent T3P (e.g., propylphosphonic
anhydride) furnished thiochondrilline C in 82% yield. The
optical rotation, NMR, and HRMS data of the synthetic
material were consistent with the reported data for the isolated
assays. The compound demonstrated moderate mouse liver
microsomal stability (t1/2 = 27 min) and good mouse plasma
stability (t1/2 = 294 min). However, it had poor permeability in
Caco-2 cells (A → B Papp = 0.11 nm/s and B → A Papp = 0.62
nm/s) and aqueous solubility (4.5 μg/mL).
In conclusion, the first synthesis of thiochondrilline C has
been accomplished using N-terminal peptide extension,
oxidative disulfide bond formation, and heterocycle installation
as key steps. The natural product was prepared in 28% overall
yield starting from 14. Several derivatives of thiochondrilline C
were also prepared. Although the natural product did not
demonstrate significant activity in the NCI 60 cancer cell line
assay, derivative 22 showed moderate antiproliferative activity
against the cell line panel, with leukemia and colon cells being
most sensitive. The activity of 22 may stem from the phenyl
ring providing a structural motif to achieve bis-intercalation.
However, this will need to be verified with more extensive SAR
and biophysical studies. Collectively, this preliminary study
supports continued optimization of thiochondrilline C
1
1
natural product. In order to demonstrate the versatility of
intermediate 5 and to examine the scope of the coupling
procedure in more detail, the structurally similar amine N-Me-
L-Ala-OMe and the primary amine (S)-1-phenylethylamine
were employed. In both cases the coupling reaction using
EDC/HOAt proceeded well to give 21 (91%) and 22 (94%) in
excellent yields.
Although thiochondrilline C’s activity in human A549 lung
adenocarcinoma cells has been reported, broader profiling of
this natural product has not been described. Therefore,
thiochondrilline C and three derivatives (5, 21, and 22) were
profiled for antiproliferative activity utilizing the National
17
Cancer Institute (NCI) 60 cancer cell line assay (Table 1).
C
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
Table 1. In Vitro Antiproliferative Activity of 22 against the NCI-60 Human Tumor Cell Lines
a
a
activity (μM)
activity (μM)
panel/cell line
Leukemia
GI50
TGI
LC50
>50
panel/cell line
Melanoma
GI50
TGI
LC50
CCRF-CEM
HL-60(TB)
K-562
1.9 ± 0.2
1.2 ± 0.1
0.7 ± 0.0
0.9 ± 0.2
5.7 ± 0.2
0.2 ± 0.1
10.5 ± 0.6
5.1 ± 1.7
3.1 ± 0.1
3.3 ± 0.2
21.6 ± 2.1
1.2 ± 0.9
SK-MEL-2
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
Ovarian Cancer
IGROVI
2.6 ± 0.4
0.9 ± 0.2
0.6 ± 0.1
8.3 ± 3.3
5.7 ± 1.2
10.1 ± 0.6
9.9 ± 1.0
3.8 ± 0.0
27.8 ± 13.0
13.3 ± 1.6
27.1 ± 0.1
31.8 ± 5.3
15.6 ± 0.2
>50
38.8 ± 1.5
> 50
MOLT-4
RPMI-8226
SR
> 50
> 50
30.2 ± 2.0
> 50
Non-Small-Cell Lung
A549/ATCC
EKVX
4.0 ± 3.0
0.6 ± 0.1
8.0 ± 0.9
5.2 ± 2.8
5.2 ± 0.5
11.0 ± 0.2
5.8 ± 1.4
12.9 ± 3.8
1.4 ± 0.0
18.4 ± 1.8
12.6 ± 3.7
17.8 ± 1.3
>50
37.6 ± 1.8
3.1 ± 0.1
42.4 ± 3.7
29.6 ± 3.6
>50
7.1 ± 0.4
3.8 ± 1.5
12.2 ± 3.5
9.7 ± 1.0
8.9 ± 0.6
5.2 ± 0.6
7.1 ± 1.0
1.3 ± 0.0
3.6 ± 1.9
15.7 ± 1.1
11.8 ± 0.9
21.0 ± 3.9
18.6 ± 1.3
17.4 ± 1.1
12.6 ± 0.8
20.1 ± 3.6
8.0 ± 0.8
35.3 ± 3.0
31.4 ± 0.9
36.8 ± 2.6
35.6 ± 1.6
34.2 ± 1.9
29.7 ± 1.0
>50
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
HOP-62
HOP-92
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
Colon Cancer
COLO 205
HCC-2998
HCT-116
HCT-15
>50
21.3 ± 2.6
>50
Renal Cancer
786-0
30.5 ± 7.0
29.1 ± 2.4
2.5 ± 0.3
15.0 ± 0.6
4.9 ± 1.6
7.3 ± 0.2
1.3 ± 0.1
5.6 ± 0.2
8.1 ± 0.0
5.8 ± 0.6
9.8 ± 1.1
33.5 ± 0.2
13.0 ± 2.3
18.5 ± 0.1
3.1 ± 0.4
14.1 ± 0.2
15.4 ± 0.1
13.3 ± 1.0
33.5 ± 4.0
>50
10.5 ± 2.6
A498
ACHN
31.5 ± 4.5
47.4 ± 0.6
13.0 ± 4.1
35.4 ± 2.2
29.7 ± 0.5
30.8 ± 1.6
1.0 ± 0.0
7.9 ± 2.3
1.8 ± 0.7
2.6 ± 0.4
1.2 ± 0.3
0.6 ± 0.0
1.9 ± 0.1
2.3 ± 0.0
17.9 ± 5.6
6.0 ± 3.1
9.7 ± 1.2
3.9 ± 1.9
8.6 ± 0.2
6.3 ± 0.7
7.2 ± 0.3
>50
CAKI-1
RXF 393
18.3 ± 6.9
25.9 ± 3.9
12.4 ± 8.0
28.3 ± 3.9
33.2 ± 9.2
SN12C
TK-10
HT29
UO-31
KM12
Prostate Cancer
PC-3
SW-620
6.1 ± 1.0
5.8 ± 0.4
13.5 ± 1.3
12.7 ± 0.5
30.3 ± 0.6
27.7 ± 0.3
CNS Cancer
SF-268
DU-145
0.4 ± 0.1
7.4 ± 0.1
2.0 ± 1.2
7.3 ± 1.0
7.7 ± 1.3
2.5 ± 0.8
11.1 ± 1.3
16.3 ± 0.2
9.4 ± 2.4
19.5 ± 1.8
>50
35.6 ± 3.8
35.8 ± 0.3
27.3 ± 4.5
>50
Breast Cancer
MCF7
SF-295
0.9 ± 0.1
1.9 ± 0.1
11.3 ± 1.5
6.9
2.6 ± 0.7
7.9 ± 0.5
34.5 ± 5.5
16.1
16.1 ± 11.2
26.0 ± 0.3
>50
SF-539
MDA-MB-231/ATCC
HS 578T
BT-549
SNB-19
SNB-75
>50
37.6
U251
7.7 ± 2.0
20.4 ± 3.0
T-47D
1.1 ± 0.0
6.0 ± 0.9
3.8 ± 0.4
13.3 ± 1.7
24.8 ± 1.0
29.8 ± 3.0
Melanoma
LOX IMVI
MALME-3M
M14
MDA-MB-468
a
0.7 ± 0.0
6.1 ± 0.0
0.3 ± 0.1
0.8 ± 0.3
1.5 ± 0.2
14.0 ± 0.5
10.3 ± 3.3
6.6 ± 0.8
3.6 ± 0.6
32.3 ± 2.1
>50
GI : concentration causing 50% growth inhibition. TGI: concen-
50
tration causing total growth inhibition. LC : concentration causing
50% net cell killing. Average values ± SEM from two independent
determinations.
50
MDA-MB-435
22.0 ± 0.4
derivatives as antiproliferative agents utilizing the versatile
synthetic method now established.
(relative intensity) for the molecular ion [M]. Optical rotations were
measured on ATAGO’s polarimeter (POLAX-2L). Specific rotation
−1
2
−1
[
α] values are given in units of 10 deg cm g .
D
2
-Aminobenzaldehyde (10). To a solution of 2-nitrobenzalde-
EXPERIMENTAL SECTION
■
hyde (1.51 g, 10 mmol) in ethanol (30 mL) and water (7.5 mL) was
added iron powder (5.6 g, 100 mmol) and concentrated HCl (0.1
mL). The reaction mixture was refluxed for 90 min, diluted with ethyl
acetate, and dried over anhydrous sodium sulfate. The insoluble
materials were removed by filtration, and the filtrate was concentrated.
The residue was purified by column chromatography on silica gel
(EtOAc/hexane, 20:80) to give 10 (1.05 g, 87%) as a pale yellow solid:
mp 38−40 °C (lit. 38−40 °C); H NMR (400 MHz, CDCl ) δ 9.87
(s, 1H), 7.48 (dd, J = 1.8, 7.8 Hz, 1H), 7.34−7.29 (m, 1H), 6.77−6.73
(m, 1H), 6.65 (d, J = 8.2 Hz, 1H), 6.12 (brs, 2H); 1 C NMR (100
General Experimental Procedures. All reactions involving air-
sensitive reagents were carried out with magnetic stirring and oven-
dried glassware with rubber septa under argon, unless otherwise stated.
All commercially available chemicals and reagent-grade solvents were
used directly without further purification, unless otherwise specified.
Reactions were monitored by thin-layer chromatography (TLC) on
Baker-flex silica gel plates (IB2-F) using UV-light (254 and 365 nm)
detection or visualizing agents (e.g., iodine, ninhydrin, or phospho-
molybdic acid stain). Flash chromatography was conducted on a silica
gel (230−400 mesh) or C column using a Teledyne ISCO
1
2
1
3
3
MHz, CDCl ) δ 194.1, 149.8, 135.7, 135.2, 118.8, 116.4, 116.0.
1
8
3
CombiFlash Rf. Melting points were measured using a Thomas-
Hoover Uni-Melt capillary melting point apparatus and are
uncorrected. NMR spectra were recorded at room temperature
Ethyl 3-Amino-2-quinolinecarboxylate (11). To a solution of
pyridine (685 mg, 8.68 mmol) in ethanol (24 mL) was added a
solution of ethyl bromopyruvate (1.69 g, 8.68 mmol) in ethanol (16
mL) dropwise. The resulting mixture was heated at 60 °C for 1 h and
then allowed to cool to room temperature. 2-Aminobenzaldehyde (1 g,
8.26 mmol) and pyridine (1.6 mL) were added to the reaction
mixture, which was then refluxed for 5 h. Pyrrolidine (1.41 g, 19.8
mmol) was added to the reaction mixture, which was then heated at 70
1
using a JEOL ECA-500 or -400 instrument ( H NMR at 500 or 400
MHz and 13C NMR at 125 or 100 MHz) with tetramethylsilane as an
internal standard. High-resolution mass spectra (HRMS) were
obtained from University of Connecticut mass spectral facility using
an AccuTOF-DART or Qstar Elite-ESI and are reported as m/z
D
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
°
C for 2 h. The reaction mixture was allowed to cool and then
temperature. The reaction mixture was concentrated, acidified with 1
N HCl, and extracted with ethyl acetate. The organic layer was washed
with brine, dried over anhydrous Na SO , filtered, and concentrated.
concentrated. The residue was purified by column chromatography on
silica gel (EtOAc/hexane, 30:70) to obtain 11 (1.6 g, 90%) as a yellow
2
4
13
1
solid: mp 149−151 °C (lit. 148−150 °C); H NMR (400 MHz,
The residue was purified by column chromatography on silica gel
(MeOH/CH Cl , 5:95) to give 15 (265 g, 51%) as a colorless oil:
CDCl ) δ 8.05 (dd, J = 2.0, 7.6 Hz, 1H), 7.56−7.54 (m, 1H), 7.47−
3
2
2
[α]24 −53.3 (c 4.5, CHCl ) [lit. [α] −53 (c 1.0, CHCl )]; H
15
25
1
7
1
1
.40 (m, 2H), 7.35 (s, 1H), 5.60 (brs, 2H), 4.54 (q, J = 7.6 Hz, 2H),
D
3
D
3
.50 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl ) δ 167.1, 142.7,
NMR (400 MHz, CDCl ), mixture of two rotamers, δ 10.2 (brs, 1H),
3
3
41.4, 134.1, 131.2, 130.4, 128.9, 126.0, 125.1, 118.6, 62.1, 14.3;
4.80 and 4.46 (dd, J = 4.8, 10.4 Hz, 1H), 3.07 and 3.04 (d, J = 4.8 Hz,
+
13
HRMS (DART-TOF) m/z calculated for C H N O [M + H]
1H), 2.89−2.83 (m, 4H), 2.11 (s, 3H), 1.44 and 1.42 (s, 9H);
C
12
13
2
2
2
17.0977, found 217.0966.
Ethyl 3-Hydroxy-2-quinolinecarboxylate (12). Compound 11
864 mg, 4.0 mmol) was added to 3 mL of 40% sulfuric acid at room
NMR (100 MHz, CDCl ), mixture of two rotamers, δ 175.5 and 175.4,
3
156.4 and 155.2, 81.3 and 80.8, 59.5 and 57.7, 33.8 and 33.0, 32.6 and
(
31.9, 28.2, 15.7 and 15.3; HRMS (DART-TOF) m/z calculated for
+
temperature, and then 3 g of ice was added. The mixture was stirred
C H NO S [M + H] 250.1113, found 250.1116.
10
20
4
for 5 min to form a homogeneous paste. The slurry was cooled to 0−5
Methyl N,S-Dimethyl-L-cysteinate (6). To a solution of 15 (250
°
C, and then a cold solution of NaNO (304 mg, 4.4 mmol) in 1 mL
mg, 1.0 mmol) in methanol (3 mL) at 0 °C was added thionyl chloride
(131 mg, 1.1 mmol) dropwise. The reaction mixture was allowed to
warm to room temperature and stirred for 12 h. The reaction mixture
2
of water was added dropwise. The reaction mixture was stirred for 15
min and then added to a boiling solution of 50% sulfuric acid (20 mL)
dropwise. After the addition, the solution was boiled for 10 min and
poured into ice−water. The reaction mixture was neutralized with
was concentrated, quenched with saturated aqueous NaHCO , and
3
extracted with ethyl acetate. The organic layer was washed with brine,
saturated aqueous NaHCO and extracted with ethyl acetate. The
dried over anhydrous Na SO , filtered, and concentrated. The residue
3
2
4
organic layer was washed with brine, dried over anhydrous Na SO ,
filtered, and concentrated. The residue was purified by column
was purified by column chromatography on silica gel (MeOH/
2
4
2
5
CH Cl , 5:95) to give 6 (117 mg, 72%) as a colorless oil: [α] +5.4
2 2 D
15
25
1
chromatography on silica gel (EtOAc/hexane, 20:80) to give 12 (590
(c 5.5, CHCl ) [lit. [α]
+5.6 (c 1.1, CHCl )]; H NMR (400
3
3
D
1
mg, 68%) as a white solid: mp 108−109 °C; H NMR (400 MHz,
MHz, CDCl ) δ 3.77 (s, 3H), 3.39 (t, J = 6.4 Hz, 1H), 2.84−2.77 (m,
3
13
CDCl ) δ 10.55 (s, 1H), 8.16−8.13 (m, 1H), 7.73−7.70 (m, 2H),
1H), 2.42 (s, 3H), 2.13 (s, 3H); C NMR (100 MHz, CDCl ) δ
3
3
13
7
.60−7.53, 4.63 (q, J = 6.8 Hz, 2H), 1.54 (t, J = 6.8 Hz, 3H);
NMR (100 MHz, CDCl ) δ 169.2, 153.9, 142.5, 133.7, 132.0, 130.5,
C
173.9, 62.3, 51.9, 36.9, 34.6, 16.0; HRMS (DART-TOF) m/z
+
calculated for C H NO S [M + H] 164.0745, found 164.0761.
3
6
14
2
t
1
29.4, 127.5, 126.2, 120.7, 63.1, 14.2; HRMS (DART-TOF) m/z
Boc-N-Me-L-Cys(Trt)-O Bu (16). To a solution of 14 (1.0 g, 2.1
mmol) and tert-butyl-2,2,2-trichloroacetamidate (911 mg, 4.2 mmol)
in CH Cl (15 mL) was added BF ·Et O (30 mg, 0.21 mmol) at room
+
calculated for C H NO [M + H] 218.0817, found 218.0822.
12
12
3
3
-Hydroxy Quinoline-2-carboxylic acid (13). Potassium
2
2
3
2
hydroxide (336 mg, 6.0 mmol) was added to a solution of 12 (434
temperature, and then the mixture was stirred for 18 h. The reaction
mg, 2.0 mmol) in 10 mL of a 3:1:1 mixture of THF/MeOH/H O at
room temperature and stirred for 4 h. The reaction mixture was
concentrated and acidified with 1 N HCl(aq). The solid was filtered and
mixture was quenched with solid NaHCO (617 mg, 7.35 mmol) and
2
3
stirred for 10 min. The insoluble material was removed by filtration,
and the filtrate was concentrated. The residue was purified by column
chromatography on silica gel (EtOAc/hexane, 20:80) to give 16 (950
washed with ice cold water and cold Et O to afford 13 (347 mg, 92%)
2
1
8
1
27
1
as a yellow solid: mp 189−191 °C (dec) (lit. 187−190 °C); H
NMR (400 MHz, DMSO-d ) δ 8.15 (d, J = 7.6 Hz, 1H), 8.05 (s, 1H),
.96 (d, J = 8.0 Hz, 1H), 7.72−7.65 (m, 2H); C NMR (100 MHz,
DMSO-d ) δ 167.3, 152.8, 138.9, 138.5, 131.3, 129.4, 129.1, 127.2,
mg, 85%) as a colorless oil: [α] −5.2 (c 2.87, CHCl ); H NMR
D
3
(400 MHz, CDCl ), mixture of two rotamers, δ 7.45−7.42 (m, 6H),
6
3
13
7
7.31−7.26 (m, 6H), 7.23−7.18 (m, 3H), 3.85−3.75 (m, 1H), 2.87−
1
3
2.54 (m, 5H), 1.45 and 1.40 (s, 9H), 1.37 and 1.34 (s, 9H); C NMR
6
1
+
26.7, 122.9; HRMS (DART-TOF) m/z calculated for C H NO [M
H] 190.0504, found 190.0544.
Boc-N-Me-L-Cys(Trt)-OH (14). To a solution of NaH (60% in
(100 MHz, CDCl ), mixture of two rotamers, δ 169.4 and 169.2, 155.6
1
0
8
3
3
+
and 155.1, 144.63 and 144.56, 129.58 and 129.50, 127.91 and 127.88,
126.65 and 126.60, 81.6 and 81.4, 80.3 and 79.9, 66.8, 60.6 and 60.3,
33.4 and 33.3, 31.7 and 31.3, 28.32 and 28.29, 27.90 and 27.83; HRMS
mineral oil, 432 mg, 10.8 mmol) in THF (10 mL) was added Boc-
Cys(Trt)-OH (2.0 g, 4.32 mmol) in THF (3 mL) dropwise at 0−5 °C.
After 15 min MeI was added dropwise to the reaction mixture and was
stirred for 18 h. The reaction mixture was quenched with MeOH,
acidified with 1 N HCl, and extracted with ethyl acetate. The organic
layer was washed with brine, dried over anhydrous Na SO , filtered,
+
(ESI- Qstar Elite) m/z calculated for C H NNaO S [M + Na]
32
39
4
556.2497, found 556.2524.
t
N-Me-L-Cys(Trt)-O Bu (17). To a solution of 16 (950 mg, 1.78
mmol) in ethyl acetate (9 mL) was added 4 N HCl in dioxane (3 mL).
The reaction mixture was stirred for 12 h, concentrated, neutralized
2
4
and concentrated. The residue was purified by column chromatog-
raphy on silica gel (EtOAc/hexane, 40:60) to give 14 (1.42 g, 69%) as
with saturated aqueous NaHCO , and extracted with ethyl acetate.
The organic layer was washed with brine, dried over anhydrous
3
2
6
1
a white foam: [α]
−26 (c 3.33, CHCl ); H NMR (400 MHz,
Na SO , filtered, and concentrated. The residue was purified by
D
3
2
4
CDCl ), mixture of two rotamers, δ 10.81 (brs, 1H), 7.43−7.41 (m,
column chromatography on silica gel (EtOAc/hexane, 50:50) to give
3
17 (648 mg, 84%) as a colorless oil: [α]22 +22.6 (c 1.77, CHCl ); H
1
6
H), 7.28−7.17 (m, 9H), 3.93 (dd, J = 5.2 Hz, 10 Hz, 0.45), 3.61 (dd,
J = 5.2 Hz, 8.4 Hz, 0.55H), 2.85−2.80 (m, 1H), 2.67−2.58 (m, 4H),
.42 and 1.36 (s, 9H); 13C NMR (100 MHz, CDCl ), mixture of two
D
3
NMR (400 MHz, CDCl ) δ 7.44−7.41 (m, 6H), 7.29−7.26 (m, 6H),
3
1
7.22−7.18 (m, 3H), 2.83 (dd, J = 6.0 Hz, 7.2 Hz, 1H), 2.42−2.32 (m,
3
rotamers, δ 175.8 and 175.6, 155.8 and 154.7, 144.3, 129.4, 127.9,
1H), 2.26 (s, 3H), 1.41 (s, 9H); 13C NMR (100 MHz, CDCl ) δ
3
1
3
26.7, 81.1 and 80.5, 66.91 and 66.81, 60.3 and 59.2, 34.1 and 33.3,
172.5, 144.6, 129.6, 127.8, 126.6, 81.4, 66.5, 62.8, 34.6, 34.4, 28.0;
+
1.4 and 30.7, 28.2 and 28.1; HRMS (ESI-Qstar Elite) m/z calculated
HRMS (DART-TOF) m/z calculated for C H NO S [M + H]
27
32
2
+
for C H NNaO S [M + Na] 500.1871, found 500.1890.
434.2154, found 434.2140.
28
31
4
t
Boc-N-Me-L-Cys(Me)-OH (15). To a solution of 14 (1.0 g, 2.1
mmol) in dichloromethane (5 mL) were added triisopropylsilane (1.7
g, 10.5 mmol) and TFA (6.2 g, 54.6 mmol) at room temperature. The
reaction mixture was stirred for 1 h and then concentrated. The crude
reaction mixture was washed with diethyl ether and dried in vacuo to
afford a colorless oil, which was used directly in the next step. The
crude oil was dissolved in a 1:1 mixture of THF/water (20 mL) and
Fmoc-Gly-N-Me-L-Cys(Trt)-O Bu (18). To a solution of 17 (648
mg, 1.5 mmol) and Fmoc-Gly-OH (445 mg, 1.5 mmol) in DMF (7.5
mL) were added HOAt (245 mg, 1.8 mmol) and EDC (345 mg, 1.8
mmol). The reaction mixture was stirred for 3 h at room temperature
and then quenched by the addition of 1 N HCl(aq). The aqueous layer
was extracted with EtOAc (2 × 25 mL), and the combined organic
layers were washed with saturated aqueous NaHCO and brine, dried
3
was treated with NaHCO (353 mg, 4.2 mmol) and MeI (328 mg, 2.3
over anhydrous Na SO , filtered, and concentrated. The residue was
3
2
4
mmol). The reaction mixture was stirred for 3 h and then basified with
purified by column chromatography on silica gel (EtOAc/hexane,
2
6
1
2
N NaOH(aq). To the reaction mixture was added (Boc) O (550 mg,
.52 mmol); then the reaction mixture was stirred for 12 h at room
50:50) to afford 18 as a white foam (1.02 g, 96%): [α] −14.8 (c
2
D
1
2.71, CHCl ); H NMR (400 MHz, CDCl ), mixture of two rotamers,
3
3
E
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
δ 7.76 (d, J = 8.0 Hz, 2H), 7.61 (d, J = 7.2 Hz, 2H), 7.45−7.38 (m,
ice cold temperature, and quenched with saturated aqueous sodium
bisulfite. The reaction mixture was concentrated and then partitioned
8
3
H), 7.33−7.20 (m, 11H), 5.82 (m, 1H), 4.46−4.21 (m, 4H), 4.10−
13
.53 (m, 2H), 2.83−2.60 (m, 5H), 1.35 (s, 9H); C NMR (100 MHz,
between H O and EtOAc. The organic layer was washed with brine,
2
CDCl ), mixture of two rotamers, δ 168.6 and 168.5, 168.2 and 167.5,
dried over anhydrous Na SO , filtered, and concentrated. The residue
3
2
4
1
56.0 and 155.9, 144.3 and 144.1, 143.8, 141.2, 129.5 and 129.4, 128.1
was purified by column chromatography on silica gel (EtOAc/hexane,
2
4
and 128.0, 127.6, 127.0 and 126.9, 126.8, 125.2, 119.9, 83.1 and 82.3,
50:50) to afford 20 as a colorless oil (70 mg, 91%): [α] −141.66 (c
D
1
6
3
7.5 and 67.1, 67.0, 59.1 and 59.0, 47.1, 42.9 and 42.8, 32.3 and 30.3,
0.5 and 28.6, 27.84 and 27.79; HRMS (DART-TOF) m/z calculated
5.4, CHCl ); H NMR (500 MHz, CDCl ) δ 11.54 (s, 1H), 9.29 (d, J
3
3
= 5.5 Hz, 1H), 8.73 (d, J = 9.5 Hz, 1H), 8.07 (d, J = 8.0 Hz, 1H),
7.70−7.68 (m, 1H), 7.62 (s, 1H), 7.57−7.50 (m, 2H), 5.24 (dd, J =
10.0, 15.0 Hz, 1H), 5.07−5.04 (m, 1H), 4.99 (t, J = 7.5 Hz, 1H), 3.84
(dd, J = 6.0, 15.0 Hz, 1H), 3.65−3.62 (m, 1H), 3.45−3.41 (m, 2H),
+
for C H N O S [M + H] 713.3049, found 713.3066.
44
45
2
5
t
Fmoc-D-Cys(Trt)-Gly-NMe-L-Cys(Trt)-O Bu (19). To a solution
of 18 (925 mg, 1.3 mmol) in DMF (13 mL) was added piperidine
1
3
(110 mg, 1.3 mmol) at room temperature. The reaction mixture was
3.05 (dd, J = 8.0, 15.0 Hz, 1H), 2.77 (s, 3H), 1.54 (s, 9H); C NMR
stirred for 1 h, evaporated, and purified by flash column
chromatography on silica gel and then used for the next step directly.
To a solution of dipeptide and Fmoc-D-Cys(Trt)-OH (760 mg, 1.3
mmol) in DMF (6.5 mL) were added HOAt (212 mg, 1.56 mmol)
and EDC (299 mg, 1.56 mmol). The reaction mixture was stirred for 3
h at room temperature and then quenched by the addition of 1 N
HCl(aq). The aqueous layer was extracted with EtOAc (2 × 25 mL),
and the combined organic layers were washed with saturated aqueous
NaHCO and with brine, dried over anhydrous Na SO , filtered, and
(125 MHz, CDCl ) δ 170.7, 168.1, 168.0, 167.4, 153.5, 141.5, 134.0,
132.0, 129.8, 128.7, 127.2, 126.2, 120.4, 83.7, 58.8, 53.0, 43.6, 43.1,
3
40.1, 29.2, 27.9; HRMS (DART-TOF) m/z calculated for
+
C H N O S [M + H] 521.1529, found 521.1514.
23
29
4
6 2
(4R,10S)-10-(3-Hydroxyquinoline-2-carboxamido)-5-methyl-
6,9-dioxo-1,2-dithia-5,8-diazacycloundecane-4-carboxylic acid
(5). Compound 20 (62 mg, 0.12 mmol) was treated with TFA (2 mL)
for 1 h at room temperature. The reaction mixture was concentrated
and purified by column chromatography on silica gel (MeOH/
3
2
4
concentrated. The residue was purified by column chromatography on
CH
212 °C; [α] −120.2 (c 0.79, CH
CD COCD ) δ 11.75 (s, 1H), 9.33 (d, J = 6.4 Hz, 1H), 8.67 (d, J = 9.6
3
Cl , 10:90) to afford 5 as a white solid (45 mg, 82%): mp 210−
2 2
25 1
silica gel (EtOAc/hexane, 50:50) to afford 19 as a white foam (1.06 g,
D
COCH ); H NMR (400 MHz,
3 3
1
7
7%): [α]22 −11.95 (c 2.93, CHCl ); H NMR (400 MHz, CDCl ),
3
D
3
3
mixture of two rotamers, δ 7.74 (t, J = 8.4 Hz, 2H), 7.59 (t, J = 5.6 Hz,
Hz, 1H), 8.04−8.02 (m, 1H), 7.86−7.83 (m, 1H), 7.74 (s, 1H), 7.64−
7.58 (m, 2H), 5.11−5.02 (m, 3H), 3.84 (dd, J = 5.6, 14.8 Hz, 1H),
3.57 (d, J = 14.8 Hz, 1H), 3.50 (dd, J = 6.4, 15.2 Hz, 1H), 3.33 (dd, J =
2
H), 7.42−7.18 (m, 34H), 6.85 (brs, 1H), 5.09 (m, 1H), 4.38−4.19
13
(
m, 4H), 3.98−3.52 (m, 3H), 2.82−2.57 (m, 7H), 1.32 (s, 9H);
C
1
3
NMR (100 MHz, CDCl ), mixture of two rotamers, δ 169.7 and 169.5,
2.8, 15.2 Hz, 1H), 3.18 (dd, J = 8.0, 15.2 Hz, 1H), 2.74 (s, 3H);
C
3
1
1
1
6
3
68.2 and 168.0, 167.9 and 167.5, 155.7, 144.3 and 144.0, 144.3 and
43.8, 143.6, 141.2, 129.5 and 129.4, 128.1 and 128.0, 127.9, 127.6,
27.1 and 127.0, 126.9, 126.8, 125.13 and 125.11, 119.9, 83.2 and 82.3,
7.6 and 67.2, 67.1, 67.0, 59.1 and 58.9, 53.7, 47.0, 41.6 and 41.5, 34.2,
NMR (100 MHz, CD COCD ) δ 170.6, 169.5, 168.0, 167.5, 153.9,
3
3
141.4, 134.5, 132.3, 129.5, 129.0, 127.6, 126.6, 120.3, 57.8, 53.0, 43.7,
43.0, 40.1, 28.4; HRMS (DART-TOF) m/z calculated for
+
C
H
21
N
O
6
S
2
[M + H] 465.0903, found 465.0908.
19
4
2.2 and 30.3, 30.5 and 28.6, 27.82 and 27.78; HRMS (ESI- Qstar
Methyl N-((4R,10S)-10-(3-Hydroxyquinoline-2-carboxami-
+
do)-5-methyl-6,9-dioxo-1,2-dithia-5,8-diazacycloundecane-4-
carbonyl)-N-methyl-L-alaninate (21). To a solution of N-methyl-L-
alanine methyl ester (7.0 mg, 0.06 mmol) and 5 (24 mg, 0.05 mmol)
in DMF (1 mL) were added HOAt (8.5 mg, 0.06 mmol), EDC (11.5
mg, 0.06 mmol), and diisopropyl ethylamine (8.0 mg, 0.06 mmol).
The reaction mixture was stirred for 3 h at room temperature and then
quenched by the addition of 1 N HCl(aq). The aqueous layer was
extracted with EtOAc (2 × 15 mL), and the combined organic layers
Elite) m/z calculated for C H NaN O S [M + Na] 1080.4056,
66
63
3
6 2
found 1080.4014.
tert-Butyl N,N-(3-Hydroxyquinoline-2-carbonyl)-S-trityl-D-
cysteinylglycyl-N-methyl-S-trityl-L-cysteinate (7). To a solution
of 19 (1.06 mg, 1.0 mmol) in DMF (10 mL) was added piperidine (85
mg, 1.0 mmol) at room temperature. The reaction mixture was stirred
for 1 h, concentrated, purified by flash column chromatographed on
silica gel, and used for the next step directly. To a solution of tripeptide
and 13 (189 mg, 1.0 mmol) in DMF (5 mL) were added HOAt (163
mg, 1.2 mmol) and EDC (230 mg, 1.2 mmol). The reaction mixture
was stirred for 3 h at room temperature and then quenched by the
addition of 1 N HCl(aq). The aqueous layer was extracted with EtOAc
were washed with saturated aqueous NaHCO
washed with brine, dried over anhydrous Na
concentrated. The residue was purified by column chromatography on
silica gel (MeOH/CH Cl , 5:95) to give 21 as a pale yellow solid (26
mg, 90%): [α]25
−30 (c 0.5, CHCl
. The organic layer was
3
SO , filtered, and
2
4
2
2
1
(
2 × 25 mL), and the combined organic layers were washed with
D
); H NMR (400 MHz, CDCl ),
3 3
saturated aqueous NaHCO and with brine, dried over anhydrous
mixture of two rotamers, δ 11.37 and 11.36 (s, 1H), 8.98−8.95 (m,
1H), 8.01−7.99 (m, 1H), 7.75−7.70 (m, 2H), 7.66 (s, 1H), 7.59−7.52
(m, 2H), 5.23−5.14 (m, 2H), 4.97−4.81 (m, 2H), 3.93−3.69 (m, 6H),
3
Na SO , filtered, and concentrated. The residue was purified by
2
4
column chromatography on silica gel (EtOAc/hexane, 50:50) to afford
2
7
7
as a white foam (885 mg, 88%): mp 104−106 °C; [α] +8.0 (c 5.0,
3.19−3.17 (m, 3.3H), 3.00 (s, 1H), 2.85−2.74 (m, 3.7H), 1.69 and
D
1
13
CHCl ); H NMR (400 MHz, CDCl ), mixture of two rotamers, δ
1.47 (d, J = 7.6 Hz, 3H); C NMR (100 MHz, CDCl
3
), mixture of
3
3
1
7
2
1
2
1.61 and 11.59 (s, 1H), 8.81 (d, J = 8.4 Hz, 1H), 8.01−7.99 (m, 1H),
.72−7.70 (m, 1H), 7.63 (s, 1H), 7.57−7.50 (m, 2H), 7.45−7.17 (m,
9H), 6.87 (brs, 1H), 4.33−4.24 (m, 1.7H), 3.79 (d, J = 3.6 Hz,
.35H), 3.82 (d, J = 3.6 Hz, 0.65H), 3.50 (dd, J = 4.8, 9.6 Hz, 0.3H),
two rotamers, δ 171.3, 168.92, 168.87, 168.1, 167.9, 153.5, 141.5 and
141.0, 133.7, 132.4 and 132.2, 129.6 and 129.5, 129.0, 127.6 and 127.5,
126.4, 120.7, 57.8, 54.54 and 54.50, 54.24 and 54.22, 52.8 and 52.5,
44.4 and 44.2, 43.6, 43.3, 32.2 and 30.2, 30.1 and 29.9, 16.3 and 14.4;
13
[M + H]+
.97−2.88 (m, 1H), 2.79−2.52 (m, 6H), 1.31 (s, 9H); C NMR (100
HRMS (DART-TOF) m/z calculated for C24H N O S
30 5 7 2
MHz, CDCl ), mixture of two rotamers, δ 168.9 and 168.7, 168.2,
564.1587, found 564.1609.
3
1
1
1
68.1 and 168.0, 167.9 and 167.4, 153.7, 144.3, 144.2 and 144.0, 141.4,
34.2, 132.1, 129.7, 129.6, 129.5 and 129.4, 128.7, 128.2 and 128.1,
27.9, 127.2, 127.0 and 126.9, 126.7, 126.3, 120.3, 83.2 and 82.3, 67.6
(4R,10S)-10-(3-Hydroxyquinoline-2-carboxamido)-5-methyl-
6,9-dioxo-N-((S)-1-phenylethyl)-1,2-dithia-5,8-diazacyclounde-
cane-4-carboxamide (22). To a solution of (S)-phenylethylamine
(6.5 mg, 0.05 mmol) and 5 (24 mg, 0.05 mmol) in DMF (1 mL) were
and 67.3, 67.1, 59.2 and 58.9, 51.9 and 51.8, 41.7, 34.0 and 33.9, 32.2
and 30.3, 30.5 and 28.7, 27.82 and 27.78; HRMS (ESI-Qstar Elite) m/
z calculated for C H N NaO S [M + Na] 1029.3695, found
added HOAt (8.5 mg, 0.06 mmol) and EDC (11.5 mg, 0.06 mmol).
The reaction mixture was stirred for 3 h at room temperature and then
quenched by the addition of 1 N HCl(aq). The aqueous layer was
extracted with EtOAc (2 × 15 mL), and the combined organic layers
+
61
58
4
6 2
1029.3637.
tert-Butyl (4R,10S)-10-(3-Hydroxyquinoline-2-carboxamido)-
-methyl-6,9-dioxo-1,2-dithia-5,8-diazacycloundecane-4-car-
5
were washed with saturated aqueous NaHCO
3
. The organic layer was
boxylate (20). To a solution of iodine (380 mg, 1.5 mmol) in a 10:1
mixture of dichloromethane/methanol (143 mL) was added a solution
of 7 (150 mg, 0.15 mmol) in dichloromethane (40 mL) dropwise at
room temperature. The reaction mixture was stirred for 1 h, cooled to
washed with brine, dried over anhydrous Na SO , filtered, and
2
4
concentrated. The residue was purified by column chromatography on
silica gel (EtOAc/hexane, 50:50) to give 22 as a pale yellow solid (27
26
D
1
mg, 94%): mp 146−148 °C; [α] −43.3 (c 2.08, CHCl ); H NMR
3
F
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
(
(
400 MHz, CDCl ) δ 11.43 (s, 1H), 9.13 (d, J = 3.2 Hz, 1H), 8.41
brs, 1H), 8.00 (d, J = 7.6 Hz, 1H), 7.71−7.68 (m, 1H), 7.63 (s, 1H),
.58−7.51 (m, 2H), 7.37−7.28 (m, 6H), 5.12−5.08 (m, 2H), 4.97
50, 734−737. (b) Baz, J. P.; Can
̃
edo, L. M.; Fernan
́
dez-Puentes, J. L. J.
3
Antibiot. 1997, 50, 738−741.
7
(7) Erba, E.; Bergamaschi, D.; Ronzoni, S.; Faretta, M.; Taverna, S.;
Bonfanti, M.; Catapano, C. V.; Faircloth, G.; Jimeno, J.; D’Incalci, M.
Br. J. Cancer 1999, 80, 971−980.
(
brs, 1H), 4.77 (t, J = 7.2 Hz, 1H), 3.76 (dd, J = 6.4, 14.4 Hz, 1H),
3
2
.62 (d, J = 14.8 Hz, 1H), 3.41 (brs, 1H), 3.29 (d, J = 14.8, 1H), 3.09−
13
.95 (m, 1H), 2.96 (s, 1H), 1.57 (d, J = 6.8 Hz, 3H); C NMR (125
(8) Wang, Y.; Liu, Y.; Malek, S. N.; Zheng, P.; Liu, Y. Cell Stem Cell
2011, 8, 399−411.
MHz, CDCl ) δ 169.7, 168.6, 167.9, 167.3, 153.5, 142.3, 141.5, 133.9,
3
1
32.1, 129.8, 128.9, 128.7, 127.6, 127.4, 126.3, 120.6, 58.4, 53.2, 49.4,
(9) Boger, D. L.; Ichikawa, S.; Tse, W. C.; Hedrick, M. P.; Jin, Q. J.
Am. Chem. Soc. 2001, 123, 561−568.
4
3.9, 43.3, 41.0, 30.0, 22.0; HRMS (DART-TOF) m/z calculated for
+
C H N O S [M + H] 568.1688, found 568.1696.
(10) Negri, A.; Marco, E.; García-Hernan
Llamas-Saiz, A. L.; Porto-Sanda,
Cordonnier, M.-H.; Bailly, C.; García-Fernan
́
dez, V.; Domingo, A.;
S.; Riguera, R.; Laine, W.; David-
dez, L. F.; Vaquero, J. J.;
27
30
5
5 2
Thiochondrilline C (4). To a solution of 6 (17 mg, 0.1 mmol), 5
24 mg, 0.05 mmol), and diisopropyl ethylamine (13 mg, 0.1 mmol) in
́
(
́
DMF (1 mL) was added T3P (50% in DMF, 127 mg, 0.2 mmol)
dropwise at 0 °C. The reaction mixture was stirred for 24 h and
extracted with ethyl acetate. The organic layer was washed with brine,
dried over anhydrous Na SO , filtered, and concentrated. The residue
Gago, F. J. Med. Chem. 2007, 50, 3322−3333.
(11) Wyche, T. P.; Hou, Y.; Braun, D.; Cohen, H. C.; Xiong, M. P.;
Bugni, T. S. J. Org. Chem. 2011, 76, 6542−6547.
(12) Diedrich, C. L.; Haase, D.; Saak, W.; Christoffers, J. Eur. J. Org.
Chem. 2008, 2008, 1811−1816.
2
4
was purified by column chromatography on silica gel (MeOH/
CH Cl , 10:90) and then by reversed-phase C -column (MeOH/
H O, 60:40) to afford thiochondrilline C as a white solid (26 mg,
2
2
18
(13) Wang, Y. D.; Boschelli, D. H.; Johnson, S.; Honores, E.
Tetrahedron 2004, 60, 2937−2942.
2
2
3
11
25
8
2%): [α] −76.0 (c 0.46, CHCl ) [lit. [α] −77.0 (c 0.0011,
D
3
D
(14) Patel, H. M.; Tao, J.; Walsh, C. T. Biochemistry 2003, 42,
10514−10527.
1
CHCl )]; H NMR (400 MHz, CDCl ), mixture of rotamers, δ 11.45
3
3
and 11.38, 9.15, and 8.96 (d, J = 8.4 Hz, 1H), 7.99 (d, J = 8.0 Hz, 1H),
(
15) Boger, D. L.; Ichikawa, S. J. Am. Chem. Soc. 2000, 122, 2956−
7
7
4
.91 (brd, J = 9.6 Hz, 1H), 7.74−7.70 (m, 1H), 7.65 (s, 1H), 7.60−
.52 (m, 2H), 5.30−5.15 (m, 2H), 5.08 (dd, J = 4.0, 11.2 Hz, 1H),
.90 (brt, J = 8.0 Hz, 1H), 3.96 (brs, 1H), 3.83−3.76 (m, 4H), 3.70
2
957.
16) Kamber, B.; Hartmann, A.; Eisler, K.; Riniker, B.; Rink, H.;
(
Sieber, P.; Rittel, W. Helv. Chim. Acta 1980, 63, 899−915.
(
dd, J = 9.6, 14.4 Hz, 1H), 3.30−3.13 (m, 5H), 2.97−2.90 (m, 4H),
(
(
17) Shoemaker, R. H. Nat. Rev. Cancer 2006, 6, 813−823.
2
.78 (brd, J = 11.6 Hz, 1H), 2.40 and 2.14 (s, 3H); 13C NMR (125
MHz, CDCl ) δ 169.9, 168.9 (2C), 168.6, 167.9, 153.5, 141.5, 133.8,
́
18) Riego, E.; Bayo,
́
N.; Cuevas, C.; Albericio, F.; Alvarez, M.
3
Tetrahedron 2005, 61, 1407−1411.
1
4
32.2, 129.6, 128.9, 127.5, 126.4,120.7, 57.9, 57.7, 54.3, 52.7, 44.3,
3.8, 43.3, 32.9, 32.8, 30.5, 15.6; HRMS (DART-TOF) m/z calculated
+
for C H N O S [M + H] 610.1464, found 610.1471.
25
32
5
7 3
ASSOCIATED CONTENT
Supporting Information
■
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.jnat-
prod.5b00428.
NMR spectral data of 4, 5, 7, 12, 14, and 16−22, as well
as the LC-MS of 4 (PDF)
AUTHOR INFORMATION
Corresponding Author
Tel: +01-713-743-1274. E-mail: gdcuny@central.uh.edu.
■
*
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors would like to thank the University of Houston for
financial support and the National Cancer Institute for testing
the compounds in the 60 cell line assays.
REFERENCES
■
(
2
1) Zolova, O. E.; Mady, A. S. A.; Garneau-Tsodikova, S. Biopolymers
010, 93, 777−790.
(
2) Gradishar, W. J.; Vogelzang, N. J.; Kilton, L. J.; Leibach, S. J.;
Rademaker, A. W.; French, S.; Benson, A. B., 3rd Invest. New Drugs
995, 13, 171−174.
3) Tulla-Puche, J.; Auriemma, S.; Falciani, C.; Albericio, F. J. Med.
Chem. 2013, 56, 5587−5600.
4) Zamudio-Vazquez, R.; Albericio, F.; Tulla-Puche, J.; Fox, K. R.
ACS Med. Chem. Lett. 2014, 5, 45−50.
5) Lombo, F.; Velasco, A.; Castro, A.; de la Calle, F.; Brana, A. F.;
Sanchez-Puelles, J. M.; Mendez, C.; Salas, J. A. ChemBioChem 2006, 7,
66−376.
6) (a) Romero, F.; Espliego, F.; Baz, J. P.; de Quesada, T. G.;
Gravalos, D.; de la Calle, F.; Fernandez-Puentes, J. L. J. Antibiot. 1997,
1
(
(
́
(
3
(
́
́
G
DOI: 10.1021/acs.jnatprod.5b00428
J. Nat. Prod. XXXX, XXX, XXX−XXX